House Speaker John Boehner (R) of Ohio leaves after a photo session with members of the new 113th Congress that convened Thursday in the Capitol in Washington. Republicans have promised a fight over the debt limit in the new Congress.

J. Scott Applewhite/AP

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[Editor's note:Updated at 1:07 Eastern time.] Remember the "fiscal cliff" – that Armageddon of spending cuts and tax hikes that threatened the send the US economy back to the age of stone tools and woolly mammoth pelts? Well, if Washington is to be believed, that was just a warmup act.

The latest word from inside the Beltway is that Republicans are girding themselves for a fight on what might be called the Fiery Chasm of Fiscal Doom:

America will bump up against the debt ceiling, which allows the federal government to borrow more money, next month.

The "sequester" spending cuts to defense and domestic spending outlined in the 2011 debt-ceiling deal – and postponed by the fiscal cliff deal – come due on Feb. 28.

The stopgap bill that allows the federal government to function despite still not having a 2013 budget expires March 27.

Republicans say they will not raise the debt limit unless the increase is offset by spending cuts. Senate minority leader Mitch McConnell (R) of Kentucky hinted at their strategy when he told CBS's "Face the Nation" Sunday that if the government has to pare back services to deal with an unchanged debt limit, it would be the president's fault.

For his part, President Obama says he won't allow Republicans to hold the debt limit hostage and won't play ball. Behind the scenes, there are rumors of a "grand bargain" that could tie up all the outstanding issues in a nice bow.

So why does Congress lurch from crisis to crisis, seemingly propelled by the Republicans' demand to take a pound (or more) of spending flesh at every turn?

Actually, the answer is quite simple – and, at its core, it is not a matter of political posturing or point-winning, however often it devolves into that. The cause is Congress's continued unwillingness to deal with Medicare, Social Security, and the Pentagon.

The fact is, despite all the hubbub of the past two years, the federal government has still not made any meaningful spending cuts. And that is mostly because meaningful spending cuts are virtually impossible without addressing entitlements or the Department of Defense.

Congress and the president tried to do just that in the 2011 debt-ceiling deal, yet the fiscal cliff deal shows that Washington, when faced with such cuts, apparently doesn't have the stomach to let them take effect.

So Republicans sent to Washington specifically to rein in government spending have next to nothing to show for it. And the mounting fear is that they might never have anything to show for it – that the classic Washington inertia to do nothing is slowly consuming the energy of the 2010 tea party revolution.

Senator McConnell added Sunday: "Now it's time to pivot to the single biggest threat to our country, both in the short term and the long term ... and that's reducing spending."

Indeed, some Republicans are growing increasingly desperate. They believe that Congress will never get serious about bringing its spending into line unless it is in crisis. So better to manufacture one now, and solve the problem, they say, than to let things linger and eventually become Greece.

At the same time, Washington knows that responsible, long-term fiscal planning cannot move forward until spending is brought under control – it's just that the prospect of entitlement reform or Pentagon cuts are so politically unsavory that the day of reckoning is postponed again and again.

But signs are that it is coming. Credit-rating agency Moody’s has said that “the US's credit rating could be affected ‘negatively’ if Washington fails to take further steps to rein in the deficit.” All parties know the US cannot risk further downgrades to its credit rating.

Moreover, a recent Politico poll found that 75 percent of Americans wanted to rein in deficits by cutting government spending "across the board" (though other polls have shown Americans unsupportive of changes to Medicare and Social Security).

Of course, the Republicans' kamikaze approach to entitlement cuts (with little scrutiny of the Pentagon budget) is not the only option. Reportedly, fiscal-cliff talks brought Mr. Obama and House Speaker John Boehner (R) of Ohio close to a grand bargain that would have included $900 billion in spending cuts – including $600 billion in entitlement reform. But Obama wanted a significant amount of tax revenue in addition to these cuts – more than Mr. Boehner could countenance.

And that appears to be the issue going forward. Obama wants more tax revenue to accompany any entitlement reform, probably in the form of limiting tax breaks. Boehner and Republicans say they gave Obama tax revenue in the fiscal-cliff deal but got no spending cuts, meaning now is the time for cuts alone.

McConnell said as much Sunday. The debate over taxes on Capitol Hill "is over," he told "Face the Nation," adding that Democrats' desire to keep them on the table "underscores the voracious appetite for more taxes on the other side."

But the deeper point is that, with health-care expenses rising and America's baby boomer population putting stresses on Medicare and Social Security, entitlement reform appears inevitable. Congress's current cycle of crisis, then, appears merely to be the way that Washington comes a difficult decision in an age of red state bloggers, blue state pundits, and disgruntled Americans in the middle.